1. The hue of each batch or the same batch is inconsistent
(1) During the first proofing, the blade angle and ink ratio must be recorded in detail.
(2) Pre-printing control. Since spot color inks are usually prepared by themselves, it is necessary to ensure the deviation of the inks used and the ratio is accurate. The ink trays, ink sticks and ink pumps must be cleaned up. The remaining ink used last time should be added to the new ink in an appropriate amount. Adjust the scraper to record according to the record. The viscosity of the ink.
(3) The viscosity of the ink must be well controlled during printing. It is recommended to increase the number of manual measurements or prepare an automatic tracking regulator for dip.
2. Uneven transfer of ink
(1) The color of the ink should be reduced as much as possible during the color mixing. The two colors can be used instead of the three colors. The inks of different manufacturers can not be mixed. After the mixing, they must be fully stirred evenly and the appropriate butanone should be added Dissolve. When adding the solution, it should be added slowly and stirred evenly to avoid the impact of the solution causing the solubility to deteriorate, destroying the ink structure and causing poor transfer.
(2) Reduce the blade angle and blade pressure (more applicable to transition spot colors).
(3) Watermark
Increase the viscosity of the ink, because the spot color version is deeply recessed, generally 30-35um, so the ink is too low, water marks will appear, it is recommended to use a speed of 120-150m / min for 22 seconds-20 seconds cup)
3. Indented twill
(1) Reduce the pressure of the indentation roller.
(2) The rubber of the impression roller is soft, and the replaced impression roller has a hardness of 75 Shore.
4. Insufficient peel strength and speed
Because spot colors generally account for 40% -60% of the entire package, or even more. Therefore, the peel strength of the spot color must be good, which can be controlled from the following aspects.
(1) The surface tension of the substrate must meet the requirements, not less than 38 dynes / cm.
(2) Use ink suitable for the substrate model.
(3) Use a solvent with a low surface tension to reduce the surface tension of the entire ink system, thereby improving the wettability of the substrate.
(4) Increase the amount of heat and air in the oven. If the amount of heat in the oven is small, the amount of air is small, and the amount of ink on the spot color is large, which will cause insufficient adhesion and peeling.
In short, to control the printing of spot colors, it is also necessary to conscientiously summarize and improve the operator's understanding of product quality, carefully control each gate, and strive for excellence.
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